PSLE Dana hung some identical rings vertically. The thickness of each ring was 2 cm. The figure shows how the rings are connected.
- What was the distance from the top of the 1st ring to the bottom of the 6th ring?
- The distance from the top of the 1st ring to the bottom of the last ring was 134 cm. How many rings did Dana hang altogether?
(a)
Distance of 1 ring = 14 cm = 1 x 10 + 4
Distance of 2 rings = 24 cm = 2 x 10 + 4
Distance of 3 rings = 34 cm = 3 x 10 + 4
Distance from the top of the 1st ring to the bottom of the 6th ring
= 6 x 10 + 4
= 64 cm
(b)
Formula
Distance from the top of the 1st ring to the bottom of the last ring = Number of rings x 10 + 4
Number of rings x 10 + 4 = 134
Number of rings x 10 = 134 - 4
Number of rings x 10 = 130
Number of rings = 130 ÷ 10
Number of rings = 13
Number of rings that Dana hung altogether = 13
Answer(s): (a) 64 cm; (b) 13